Re: [RFC] Potential issue with GPIO/IRQ flags

[Andrew F. Davis]

On 09/16/2015 08:26 PM, Rob Herring wrote:
> On Wed, Sep 16, 2015 at 4:07 PM, Andrew F. Davis <afd@xxxxxx> wrote:
> > Hello all,
> >
> > I've noticed that in a few DT bindings GPIO_ACTIVE_* defines are
> > incorrectly used as interrupt flags. GPIO_ACTIVE_*'s are defined
> > in:
> >
> > include/dt-bindings/gpio/gpio.h
> >
> > and are used to describe GPIO pins. IRQ types are defined in:
> >
> > include/dt-bindings/interrupt-controller/irq.h
> >
> > and are flags for IRQ pins.
>
> It is perfectly valid for the meaning of the field to be defined by
> the interrupt controller, and gpio interrupts could do something
> different. We've tried to standardize this though.

Sure, but in this case these are not what the interrupt controller
is expecting.

> > These seem to have been mixed up in a few places, take for example:
> > arch/arm/boot/dts/tegra124-jetson-tk1.dts. On line 1393 we see the
> > correct usage, but just before on line 1384 we see the issue.
> > GPIO_ACTIVE_HIGH is defined as 0, the same as IRQ_TYPE_NONE. If
> > this IRQ was not hard-coded with the correct edge in the driver
> > this would not work. What the author probably wanted was
> > IRQ_TYPE_LEVEL_HIGH.
> >
> > Now lets look at commit c21e678b256b, in this the IRQ flags did not
> > matter as the correct flag was hard-coded (IRQF_TRIGGER_LOW), this
> > patch moves this to the DT, but changed the flag to GPIO_ACTIVE_LOW
> > instead of the desired IRQ_TYPE_LEVEL_LOW. GPIO_ACTIVE_LOW is defined
> > as 1, or IRQ_TYPE_EDGE_RISING in IRQ flags, which is not the
> > equivalent to IRQF_TRIGGER_LOW the author was probably looking for.
> >
> > A quick grep (git grep "interrupt.*GPIO_ACTIVE_") shows several more
> > instances of this. I found this by using one of these files as an
> > example and giving myself a lot of problems, so I would like to fix
> > this before it spreads anymore.
> >
> > I have a couple of ideas of how to go at this, first would be to
> > just replace the incorrect flags with what was intended, but for
> > some of these I don't know what was intended and do not have the
> > board to test.
> >
> > My other solution would be to just change all instances of the GPIO
> > flags to their value corresponding IRQ flags:
> >
> > - interrupts = <11 GPIO_ACTIVE_LOW>;
> > + interrupts = <11 IRQ_TYPE_EDGE_RISING>;
> >
> > this would not make any functional change as the defines would
> > still evaluate to the same value, but would make it obvious where
> > a problem may be and that they should probably be checked and
> > corrected, maybe we could even put a comment after:
> >
> > - interrupts = <11 GPIO_ACTIVE_LOW>;
> > + interrupts = <11 IRQ_TYPE_EDGE_RISING>; // FIXME: Check IRQ type
> >
> > Well, what do you think?
>
> This seems fine. It is no less wrong.

I'm not sure what you mean here.

Regards,
Andrew

> Rob
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